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1 Department of Radiology, Cincinnati Children's Hospital Medical Center, 3333
Burnet Ave., Cincinnati, OH 45229-3039.
2 Institut de Diagnostic per la Imatge, Barcelona, Spain 08035.
3 Hospital Infantil Joana de Gusmao, Florianopolis, Santa Catarina, Brazil CEP
88015-390.
4 Department of Radiology, Duke University Medical Center, Durham, NC
27710.
5 Department of Radiology, University of Michigan, Ann Arbor, MI 48103.
6 Department of Radiology, Wake Forest University, Winston Salem, NC
27157-1088.
7 Department of Radiology, Children's Hospital, Boston, MA 02115.
Received June 21, 2002;
accepted after revision August 12, 2002.
Address correspondence to L. F. Donnelly.
Abstract
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MATERIALS AND METHODS. Criteria for inclusion in the study group included neonates with a history of prematurity who required ventilation for lung disease, developement of hyperexpanded radiolucent lung lesions after typical radiographic findings of pulmonary interstitial emphysema, and CT documentation of lung abnormalities. Radiographs and CT scans were reviewed for the anatomic distribution, appearance, and presence of classic lines or dots within a radiolucent mass. We compared the management (surgical vs nonsurgical) and the temporal course in nonsurgical cases for patients in the United States and patients outside the United States.
RESULTS. From seven institutions, we identified 17 patients who had persistent pulmonary interstitial emphysema with CT documentation. On CT, all lesions consisted of hyperexpanded cystic radiolucencies. Distribution was single-lobe in nine patients (left upper lobe, n = 5; left lower lobe, n = 3; right middle lobe, n = 1), multilobar in eight patients, and bilateral in six patients. Fourteen patients (82%) showed the characteristic line-and-dot pattern. All patients were initially treated conservatively; nine eventually underwent surgical resection with confirmation at pathology. Of 10 patients who underwent nonsurgical treatment for at least 1 year, lesions resolved in four patients, decreased in size in three asymptomatic patients, and enlarged in three patients, with eventual resection in two. Surgical resection was performed in 89% (8/9) of patients treated in the United States and in 13% (1/8) of patients treated outside the United States.
CONCLUSION. Our study found that 82% of patients with persistent pulmonary interstitial emphysema had characteristic CT findings (central lines and dots surrounded by radiolucency). Although most patients in this series eventually underwent surgical resection, initial treatment can be conservative. The decision to perform surgery may have reflected the local medical culture.
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Several series have suggested that persistent pulmonary interstitial emphysema has a typical CT appearance [1, 2] and that this appearance is distinct from that of pulmonary emphysema [8, 9]. On CT, persistent pulmonary interstitial emphysema is associated with solid linear or dotlike structures within air-filled cysts [1, 2]. These solid structures are thought to represent the bronchovascular bundles surrounded by interstitial gas [1, 2]. Because the reported imaging experience with persistent pulmonary interstitial emphysema is limited, the purpose of this study was to evaluate its CT appearance, management, and outcome in a large series of patients.
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We reviewed the radiographs and CT scans in the identified patients. CT scans were reviewed for anatomic (lobar) distribution and appearance. The presence of soft tissue–density linear and punctuate structures (line-and-dot pattern) within a radiolucent mass was noted. For each patient, we recorded the age at development of pulmonary interstitial emphysema and the subsequent development of the cystic masses of persistent pulmonary interstitial emphysema. We also noted the length of time between development of persistent pulmonary interstitial emphysema and either surgical resection or last available clinical follow-up.
Certain clinical parameters were recorded, including whether the initial treatment was conservative and, if it was eventually performed, the timing of surgery. Regarding the patients treated conservatively for at least 1 year, we evaluated the temporal course of the lesions by determining whether the patients remained symptomatic, whether they eventually underwent surgery, and what was the appearance of their lungs at followup imaging. We reviewed the available follow-up CT scans and chest radiographs and noted whether the lesion resolved, decreased in size, increased in size, or remained unchanged. The frequency of surgical management was compared between patients treated in the United States and those treated outside the United States.
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On chest radiography and CT, all lesions appeared as hyperexpanded cystic radiolucencies with multiple, thin-walled cysts (Figs. 1A, 1B, 2A, 2B, 3A, 3B, 3C, 4A, 4B). Fourteen (82%) of the 17 patients showed the characteristic line-and-dot pattern (Figs. 1A, 1B, 2A, 2B, 3A, 3B, 3C).
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Anatomic distribution was within a single lobe in nine patients, including the left upper lobe in five, the left lower lobe in three, and the right middle lobe in one. Persistent pulmonary interstitial emphysema was multilobar in eight patients, and bilateral in six patients. Of the eight multilobar cases, three lobes were involved in five patients and two lobes, in three patients.
All patients were initially treated conservatively. Nine eventually underwent surgical resection, with confirmation at pathology. The anatomic distribution suggested by CT was confirmed at surgery in all patients. Indications for surgery included unmanageable respiratory distress caused by mass effect or the increasing size of lesions over a prolonged period in symptomatic patients.
Among the 10 patients who underwent nonsurgical treatment for at least 1 year, lesions as well as symptoms resolved in four patients, and lesions decreased in size in three patients whose symptoms resolved. Lesions enlarged in three patients (Fig. 4A, 4B); two eventually underwent resection, and the third patient was treated without surgery because the patient's symptoms were stable and the lesions were bilateral. At the time this article was accepted, all patients who were treated without surgery were being followed clinically and were asymptomatic.
Surgical resection was performed in 89% (8/9) of patients treated at institutions in the United States and in 13% (1/8) of patients treated outside the United States.
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The radiographic presence of pulmonary interstitial emphysema serves as a warning sign of other complications of barotrauma, such as pneumothorax. In most patients, pulmonary interstitial emphysema is transient, lasting only for several days [1, 2, 3, 4, 5, 6, 7]. Rarely, pulmonary interstitial emphysema can persist and form expanding, radiolucent masses. The fact that, in this series, only 17 patients were identified from seven large pediatric centers reflects the uncommon nature of persistent pulmonary interstitial emphysema.
Two clinical issues may arise in relation to persistent pulmonary interstitial emphysema. First, the bullous mass can expand to the extent that the mass compresses the lungs and causes respiratory compromise. The second concern is the need to differentiate persistent pulmonary interstitial emphysema from other causes of cystic radiolucent masses in neonates [1, 2].
Much recent attention has been paid to the potential risks of radiation exposure associated with the use of CT in children [11, 12, 13]. This risk is particularly true for infants, who are as much as 10 times more radiosensitive to carcinogenic effects than are adults [11]. Therefore, CT should be used in infants only when its benefits outweigh the risks. When CT is used, such dose-reduction practices as using a weight-based tube-current setting, increasing table speed, decreasing gantry rotation time, and using in-plane shielding of radiosensitive organs should be carried out [11, 12, 13, 14]. The use of CT in infants with persistent pulmonary interstitial emphysema has been advocated in two clinical situations: when the diagnosis is in question and when the anatomic distribution of the disease needs to be defined for surgical planning [1, 2].
Accurately differentiating persistent pulmonary interstitial emphysema from other causes of radiolucent cystic masses in neonates is important for future management. Surgical resection is the definitive treatment for lesions such as cystic adenomatoid malformation and congenital lobar emphysema [1, 2], whereas the advocated initial therapy for persistent pulmonary interstitial emphysema has been nonsurgical [1, 2, 6, 7]. In addition to placing children with persistent pulmonary interstitial emphysema on high-frequency ventilation, maneuvers that have been successfully used in the nonsurgical treatment include selective intubation of the bronchus contralateral to the persistent pulmonary interstitial emphysema [6] and decubitus positioning of the patient [7].
In many instances, because of the temporal relationship between the development of classic radiographic findings of pulmonary interstitial emphysema and the cystic masses of persistent pulmonary interstitial emphysema, the diagnosis of persistent pulmonary interstitial emphysema will not be in question. In our study, this temporal relationship was part of the inclusion criteria used as a requirement for making the diagnosis of persistent pulmonary interstitial emphysema. When the diagnosis is not clear, CT can be helpful in making the diagnosis of persistent pulmonary interstitial emphysema [1, 2]. The previously described CT findings of this condition include multiple thin-walled, air-filled cystic structures [1, 2]. The line-and-dot pattern has been considered a specific sign of persistent pulmonary interstitial emphysema [1, 2]. This finding is attributed to gas in the pulmonary interstitial space surrounding the bronchovascular bundles. The bronchovascular bundles then appear as linear or punctuate soft-tissue densities within the cystic radiolucencies [1, 2]. The vessels appear as lines or dots depending on the orientation of the vessel in relation to the plane of the CT image. In our series, this CT pattern was present in 14 (82%) of 17 patients.
A second benefit of CT in the evaluation of persistent pulmonary interstitial emphysema is the capability of delineating the anatomic extent of lung involvement for surgical planning. The large cystic masses of persistent pulmonary interstitial emphysema can distort lobar anatomy, which makes accurate definition of pulmonary lobar involvement on chest radiography difficult. CT, in comparison, accurately depicts which lobes are involved.
Persistent pulmonary interstitial emphysema has traditionally been categorized as either localized or diffuse. In the 17 patients in our series, all cases were localized, in the sense that no diffuse bilateral disease was present. The persistent pulmonary interstitial emphysema involved a single lobe in nine patients, was multilobar in eight patients, and involved the lobes bilaterally in six patients. Of the nine patients in whom a single lobe was involved, eight of the involved lobes were on the left side.
Nonsurgical management has been advocated as the initial therapy for persistent pulmonary interstitial emphysema [1, 2, 6, 7], and all patients in our series were initially treated conservatively. However, nine patients (53%) did eventually undergo surgical resection. The fact that eight (89%) of the nine patients cared for in the United States underwent surgery as compared with one (13%) of the eight patients cared for outside of the United States raises the possibility that local medical practice may be a major factor in determining whether surgery will ultimately be performed. Of those patients who were treated conservatively for at least 1 year, only two eventually underwent surgical resection. This finding suggests that most patients who were initially treated nonsurgically might have been able to remain nonoperative with conservative management.
In conclusion, CT can play a helpful role both in making the diagnosis of persistent pulmonary interstitial emphysema and in determining the anatomic distribution of lobar involvement. Most patients (82% in our study) with persistent pulmonary interstitial emphysema show characteristic CT findings (central lines and dots surrounded by radiolucency). Although most patients in this series eventually underwent surgery, initial management was conservative. The decision to perform surgery may reflect the underlying medical culture.
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